/**
 * 求两个颜色之间的渐变值
 * @param {string} startColor 开始的颜色
 * @param {string} endColor 结束的颜色
 * @param {number} step 颜色等分的份额
 * */
function colorGradient(startColor = 'rgb(0, 0, 0)', endColor = 'rgb(255, 255, 255)', step = 10) {
  const startRGB = hexToRgb(startColor, false) // 转换为rgb数组模式

  const startR = startRGB[ 0 ]

  const startG = startRGB[ 1 ]

  const startB = startRGB[ 2 ]

  const endRGB = hexToRgb(endColor, false)

  const endR = endRGB[ 0 ]

  const endG = endRGB[ 1 ]

  const endB = endRGB[ 2 ]

  const sR = (endR - startR) / step // 总差值

  const sG = (endG - startG) / step

  const sB = (endB - startB) / step

  const colorArr = []

  for (let i = 0; i < step; i++) {
    // 计算每一步的hex值
    const hex = rgbToHex('rgb(' + Math.round((sR * i + startR)) + ',' + Math.round((sG * i + startG)) + ',' + Math.round((sB *
			i + startB)) + ')')

    colorArr.push(hex)
  }
  return colorArr
}

// 将hex表示方式转换为rgb表示方式(这里返回rgb数组模式)
function hexToRgb(sColor, str = true) {
  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/

  sColor = sColor.toLowerCase()
  if (sColor && reg.test(sColor)) {
    if (sColor.length === 4) {
      let sColorNew = '#'

      for (let i = 1; i < 4; i += 1) {
        sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1))
      }
      sColor = sColorNew
    }
    // 处理六位的颜色值
    const sColorChange = []

    for (let i = 1; i < 7; i += 2) {
      sColorChange.push(parseInt('0x' + sColor.slice(i, i + 2)))
    }
    if (!str) {
      return sColorChange
    } else {
      return `rgb(${ sColorChange[ 0 ] },${ sColorChange[ 1 ] },${ sColorChange[ 2 ] })`
    }
  } else if (/^(rgb|RGB)/.test(sColor)) {
    const arr = sColor.replace(/(?:\(|\)|rgb|RGB)*/g, '').split(',')

    return arr.map(val => Number(val))
  } else {
    return sColor
  }
}

// 将rgb表示方式转换为hex表示方式
function rgbToHex(rgb) {
  const _this = rgb

  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/

  if (/^(rgb|RGB)/.test(_this)) {
    const aColor = _this.replace(/(?:\(|\)|rgb|RGB)*/g, '').split(',')

    let strHex = '#'

    for (let i = 0; i < aColor.length; i++) {
      let hex = Number(aColor[ i ]).toString(16)

      hex = String(hex).length == 1 ? 0 + '' + hex : hex // 保证每个rgb的值为2位
      if (hex === '0') {
        hex += hex
      }
      strHex += hex
    }
    if (strHex.length !== 7) {
      strHex = _this
    }
    return strHex
  } else if (reg.test(_this)) {
    const aNum = _this.replace(/#/, '').split('')

    if (aNum.length === 6) {
      return _this
    } else if (aNum.length === 3) {
      let numHex = '#'

      for (let i = 0; i < aNum.length; i += 1) {
        numHex += (aNum[ i ] + aNum[ i ])
      }
      return numHex
    }
  } else {
    return _this
  }
}

/**
* JS颜色十六进制转换为rgb或rgba,返回的格式为 rgba（255，255，255，0.5）字符串
* sHex为传入的十六进制的色值
* alpha为rgba的透明度
*/
function colorToRgba(color, alpha = 0.3) {
  color = rgbToHex(color)
  // 十六进制颜色值的正则表达式
  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/
  /* 16进制颜色转为RGB格式 */

  let sColor = color.toLowerCase()

  if (sColor && reg.test(sColor)) {
    if (sColor.length === 4) {
      let sColorNew = '#'

      for (let i = 1; i < 4; i += 1) {
        sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1))
      }
      sColor = sColorNew
    }
    // 处理六位的颜色值
    const sColorChange = []

    for (let i = 1; i < 7; i += 2) {
      sColorChange.push(parseInt('0x' + sColor.slice(i, i + 2)))
    }
    // return sColorChange.join(',')
    return 'rgba(' + sColorChange.join(',') + ',' + alpha + ')'
  } else {
    return sColor
  }
}

export default {
  colorGradient,
  hexToRgb,
  rgbToHex,
  colorToRgba
}
